The invention relates to the field of clinical laboratory automation where coded sample vessels and tubes are transferred automatically from one analysis station to another. The system needs to be able to read the tube coding information in each of the transfer phases so that samples are handled correctly and errors are minimized.
When a sample, for example a blood sample, is withdrawn from a patient into a sample or test tube, all the sample tubes used are coded with sample and patient information. The coding is generally provided in the form of a one or two dimensional barcode on a sticker which the analyst attaches to the side of the sample tube. The coding contains information on the sample and analyses to be performed on the sample. All this information between the automated sample transfer and handling system and the analyzers is collectively coordinated by the laboratory information system (LIS).
A commercial or a hospital clinical laboratory handles thousands of samples a day. It is of utmost importance that all errors in the process are minimized and the system operates reliably and smoothly. Usually sample tubes are placed on carriers moving along a track operating between the various analysis stations. The LIMS system instructs the system to convey the sample tubes to correct analyzers (analysis stations) according to the information given in the sample tube bar code and/or carrier RFID chip. Details between different systems vary, but in general there are code reading positions along the track and at every line cross sections so that the sample tubes are directed on a correct route. An example of such a system may be found in U.S. Pat. No. 5,605,218 or 6,520,313.
There are occasions in the process when the data is only read from the sample tubes, for example when the samples are moved from sampling laboratory or cold storage to automated transport and analysing system. The sample tubes are lifted with a gripper. The gripper moves down vertically to grab the tube from its cap and/or upper sidewalls. The attachment of the gripper claws and/or fingers against the tube must be secure but not too tight to break the tube. The tube is transferred horizontally to the receiving position and the gripper moves the tube down and releases the tube by opening up the claws when the tube sits securely in its place.
One type of gripper comprises two elongate gripping fingers and an actuator for moving the fingers in relation to each other. The fingers are in upright position and the movement occurs in perpendicular direction in relation to the longitudinal dimension of the fingers. The actuator may operate on pressurized air, electrically, by magnets or by any common actuating means. Such actuators are readily available and they can be equipped with suitable type of fingers for gripping the articles that are handled.
One problem related to the above described grippers is possible errors in reading the bar code on sample tubes. As the bar codes are attached to sample tubes manually and they may be quite long, the sticker with the bar code may reach close to the cap or mouth of the sample tube. In such case the fingers of the sample tube may extend over the bar code. If the bar code is partially covered by the finger, the bar code can't be read reliably. This problem has been solved by returning the sample tube to picking point, releasing the grip and rotating the gripper of tube whereafter the code is read again. This slows the process down. Slowing of the process decreased productivity but a more severe problem is danger of deterioration of samples that must be analysed and treated rapidly. Another possibility is to use a gripper having three or more thin fingers. A problem with multiple fingers is that mechanisms for moving multiple fingers are quite complicated.